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Abstract:

In a spur gear drive for driving the camshaft of an overhead valve
internal combustion engine wherein drive power is transmitted from the
crankshaft to the camshaft via spur gears mounted on the crankshaft and
the camshaft which is rotatably supported on the cylinder head, a third,
intermediate, gear is adjustably supported in the power train between
engine block-mounted gears and cylinder head-mounted gears so that
changes in the distance between the crankshaft and the camshaft can be
accommodated and, with the use of smaller gears, the spur gear drive
becomes smaller and lighter overall.

Claims:

1. Spur gear drive for an internal combustion engine having an engine
block and a cylinder head with a crankshaft (101) mounted on the cylinder
block and, a crankshaft gear (102; 202) mounted on the crankshaft (101),
at least camshaft with a first camshaft gear (112; 212) mounted on the
cylinder head, a first intermediate gear (104; 204) disposed in
engagement with the crankshaft gear (102, 202) a second intermediate gear
(106; 206) in engagement with the first intermediate gear (104, 204), and
a third intermediate gear (108; 208) in engagement with the second
intermediate gear (106, 206) for transmitting motion from the crankshaft
(101) to the camshaft (112).

2. A spur gear drive according to claim 1, wherein an oil pump gear (116;
216) is provided which is arranged, with respect to the crankshaft axis,
at a side of the crankshaft gear (102, 202) opposite the camshaft gear
(112, 212).

4. A spur gear drive according to claim 1, wherein a fuel pump gear drive
(122, 222) is provided in engagement with one of the second and third
gears (106; 206) to be driven thereby.

5. A spur gear drive according to claim 4, wherein the fuel pump gear
(122) is in engagement with the second intermediate gear (106) so as to
be driven by means of the first and the second intermediate gears (104,
106).

9. A spur gear drive according to claim 8, wherein the compressor gear
(120; 220) is driven by the first intermediate gear (104; 204).

10. A spur gear drive according to claim 1, wherein the first intermediate
gear (104) is a single gear with only one toothing.

11. A spur gear drive according to claim 1, wherein the turbo-compound
intermediate gear (126) is a single gear with only one toothing.

12. A spur gear drive according to claim 1, wherein the second
intermediate gear (106) is a double gear with two toothings.

13. A spur gear drive according to claim 1, wherein the first intermediate
gear (204) and the third intermediate gear (208) are double gears with
two toothings.

14. A spur gear drive according to claim 13, wherein the turbo-compound
intermediate gear (226) is a double gear with two toothings.

15. A spur gear drive according to claim 1, wherein a second camshaft gear
(114, 214) is provided, with the first camshaft gear (112, 212) actuating
inlet valve and the second camshaft gear (114, 214) actuating outlet
valve.

16. A spur gear drive according to claim 15, wherein a distributor gear is
provided as a fourth intermediate gear (110, 210), via which distributor
gear the first and the second camshaft gears (112, 114; 212, 214) are
driven by the third intermediate gear (108; 208).

17. A spur gear drive according to claim 1, wherein the third intermediate
gear (108) is arranged in a moveable fashion in order to compensate a
variation in the axis spacing of the first camshaft gear (112) and if
appropriate the second camshaft gear (114) with respect to the second
intermediate gear (106).

18. A spur gear drive according to claim 17, wherein the third
intermediate gear (108) is mounted on an eccentric disc (134) which can
preferably be adjusted by means of a spindle drive (140, 142).

19. A spur gear drive according to claim 1, wherein an intermediate gear
(208) bridging the interface area between the cylinder block and the
cylinder head is rotatably supported by a bearing journal (232) which is
eccentrically supported on one of the cylinder block and the cylinder
head for adjustment of the distance between the axes of this intermediate
gear (208) and an adjacent gear (210) supported by the other of the
cylinder head and the cylinder block.

20. A spur gear drive according to claim 19, wherein the bearing journal
(232) is mounted by bolts (236) extending through elongated holes (238)
formed in the bearing journal (232).

Description:

BACKGROUND OF THE INVENTION

[0001]The invention relates to a spur gear drive for an internal
combustion engine including a crankshaft gear and at least one camshaft
gear with intermediate spur gears for transferring power from the
crankshaft gear to the camshaft gear or gears.

[0002]Spur gear drives of this type are known in practice for driving
camshafts and engine auxiliary units. Such spur gear drives are used in
particular in internal combustion engines with a large displacement
volume as they are used for example in utility motor vehicles.

[0003]A spur gear drive for an internal combustion engine is also known
from DE 25 02 033 A1, wherein, a camshaft gear is driven by a crankshaft
gear via intermediate spur gears.

[0004]The gears of the spur gear drive transmit power and adapt the
rotational speed to the requirements of the auxiliary units and of a
first and, if applicable, a second camshaft. The transmission ratio
between the crankshaft and camshafts of 1:0.5 required for a four-stroke
internal combustion engine is generally realized by means of a double
gear.

[0005]Double gears are however relatively complex to produce, and
additionally require a relatively large installation space.

[0006]It is the object of the present invention to provide an improved
spur gear drive for an internal combustion engine.

SUMMARY OF THE INVENTION

[0007]In a spur gear drive for driving the camshaft of an overhead valve
internal combustion engine wherein the drive power is transmitted from
the crankshaft to the camshaft via spur gears mounted on the crankshaft
and the camshaft which is rotatably supported on the cylinder head, a
third, intermediate, gear is adjustably supported in the power train
between engine block-mounted gears and cylinder head-mounted gears so
that changes in the distance between the crankshaft and the camshaft can
be accommodated and, with the use of smaller gears, the spur gear drive
becomes smaller and lighter overall.

[0008]According to a preferred embodiment of the invention, an oil pump
for supplying the internal combustion engine with lubricant is arranged
below the crankshaft axis as viewed in the direction of the latter, and
therefore situated opposite the camshaft or camshafts with respect to the
crankshaft axis. Accordingly, the spur gear according to this preferred
embodiment is characterized in that an oil pump gear is arranged, with
respect to the crankshaft axis, opposite the crankshaft gear. It is
thereby possible for the spur gear drive to be of narrow design.

[0009]It is fundamentally possible for the oil pump gear to be driven
directly by the crankshaft gear. According to one preferred embodiment of
the invention, however, the oil pump gear is driven by the crankshaft
gear via an oil pump intermediate gear since, with such a design, the
desired transmission ratio can be realized with particularly small and
light gears.

[0010]According to a further preferred embodiment of the invention, a fuel
pump gear is provided in order that also the fuel supply to the internal
combustion engine can be provided by means of the spur gear drive. The
fuel pump gear is preferably driven by means of a first and a second
intermediate gear, so that the position of the fuel pump can be selected
such that as compact a design of the internal combustion engine as
possible is obtained. A corresponding situation applies for the drive of
a turbocompound for which, according to one preferred embodiment of the
invention, a turbo-compound gear and--more preferably--a turbocompound
intermediate gear are provided.

[0011]According to further preferred embodiments of the invention, it is
intended to provide a compressor gear for a compressor, in order to also
be able to drive a compressor with the spur gear drive. It is
particularly advantageous if the compressor gear is driven by the first
intermediate gear.

[0012]According to a particularly preferred embodiment of the invention,
the first intermediate gear is embodied as a single gear with only one
toothing. This reduces not only the required installation space and
weight but also the production expenditure.

[0013]According to a further preferred embodiment of the invention, the
turbocompound intermediate gear is embodied as a single gear with only
one toothing. The required installation space, the weight and the
production expenditure are also reduced in this way.

[0014]According to another further embodiment of the invention, the second
intermediate gear is a double gear with two toothings. By means of this
embodiment, it is possible to realize the desired transmission ratio
between the crankshaft on the one hand and the camshaft(s) on the other
hand of 1:0.5 with low weight and little required installation space.
Here, the first intermediate gear which is a single gear can be designed
with a relatively small diameter.

[0015]According to an alternative preferred embodiment of the invention,
the first and the third intermediate gears are embodied as double gears
with two toothings. Such an embodiment makes it possible to realize the
desired transmission ratio between the crank shaft on the one hand and
the camshafts on the other hand of 1:0.5 and at the same time to work
with a particularly small diameter for the compressor gear, the second
intermediate gear and the fuel pump gear.

[0016]If--as is provided according to a further preferred embodiment of
the invention--the turbocompound intermediate gear is a double gear with
two toothings, it is possible to situate the axis of the turbocompound
gear closer to the crankshaft axis, as a result of which the spur gear
drive is very compact. In addition, it is then also possible for the
turbocompound gear to have a very small diameter.

[0017]According to a further particularly preferred embodiment of the
invention, a second camshaft gear is provided in addition to the first
camshaft gear, with the first camshaft gear actuating at least one first
inlet valve and the second camshaft gear actuating at least one first
outlet valve. With such an embodiment, it is possible to combine the
advantages known from multi-valve technology with those of the invention.

[0018]If two camshaft gears are provided for two camshafts, as is provided
according to a particularly preferred embodiment of the invention, it is
advantageous to provide a distributor gear as a fourth intermediate gear,
via which distributor gear the first and the second camshaft gears are
driven by the third intermediate gear. The first and the second camshaft
gears and the fourth intermediate gear are then preferably arranged on a
cylinder head, so that when the cylinder head is assembled on a cylinder
block, only the fourth intermediate gear must be placed in engagement
with the third intermediate gear, which facilitates assembly.

[0019]According to a further aspect of the invention, it is provided that
the third intermediate gear is arranged in a moveable fashion in order to
compensate a variation in the axis spacing of the first camshaft gear and
if appropriate the second camshaft gear with respect to the second
intermediate gear. Such a variation of the axis spacing occurs in
particular when the planar surfaces of the cylinder head and/or of the
cylinder block are remachined, which is often the case in the course of
an overhaul of an internal combustion engine. According to said aspect of
the invention, a possibility is created for allowing for said variation,
so that it is possible overall to work with smaller tolerances, which
contributes to a reduction in the installation space.

[0020]For said adjustment of the axis spacing, the third intermediate gear
is preferably mounted on an eccentric disc which can be adjusted by means
of a spindle drive. Such an arrangement is particularly simple and
space-saving.

[0021]The invention will become more readily apparent from the following
description of particular embodiment thereof with reference to the
accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

[0022]FIG. 1 shows a first preferred embodiment of a spur gear drive
according to the invention,

[0023]FIG. 2 shows a second embodiment of a spur gear drive according to
the invention, and

[0025]The preferred first embodiment of a spur gear drive 100 according to
the invention as shown in FIG. 1 is provided for an internal combustion
engine that is, specifically, a diesel engine with a 10.6 liter
displacement volume. The spur gear drive 100 comprises a crankshaft gear
102 which drives a first camshaft gear 112 and a second camshaft gear 114
via a first intermediate gear 104, a second intermediate gear 106, a
third intermediate gear 108 and a fourth intermediate gear 110. The first
camshaft gear 112 serves for controlling the inlet valves, and the second
camshaft gear 114 serves for controlling the outlet valves, so that, as
it can be seen from FIG. 1, the internal combustion engine is a so-called
DOHC machine.

[0026]The camshaft gears 112, 114 are arranged for driving a first and a
second camshaft. The spur gear drive 100 extends below the crankshaft
gear 102, and at the end opposite the camshaft gears 112, 114, is
provided with an oil pump gear 116 which is driven by the crankshaft gear
102 via an oil pump intermediate gear 118.

[0027]A compressor gear 120 is driven by the first intermediate gear 104.
A fuel pump gear 122 is driven by the second intermediate gear 106. A
turbocompound gear 124 is driven by means of a turbocompound intermediate
gear 126.

[0028]While the first camshaft gear 112, the second camshaft gear 114 and
the fourth intermediate gear 110, which serves as a distributor gear, are
mounted on a cylinder head (not shown), the remaining gears are mounted
on a gear housing 128 which is preferably part of the engine block.

[0029]With regard to the individual gears, the following gear data have
been proven to be particularly advantageous, so that these data are
considered as relating to a particularly preferred embodiment of the
invention:

[0030]In the above table, the variable t represents the number of teeth of
the relevant gear, with a further embodiment being indicated in
parenthesis.

[0031]According to the invention, and in particular according to the
preferred embodiment of the invention described above, there is a
resulting advantage of a relatively small first intermediate gear 104. In
addition, the first intermediate gear 104 is arranged within the contour
of the engine block. One gear fewer is required than in comparable spur
gear drives. All the gears can and do preferably have straight toothings,
which facilitates assembly. In addition, the flywheel housing flange on
the housing block can be reduced in size. The oil pump rotational
direction is reversed. The above-described embodiment can also be used
for relatively large internal combustion engines, for example for a 12.8
l diesel unit.

[0032]The second embodiment shown in FIG. 2 of a spur gear transmission
200 according to the invention is provided, like the first embodiment,
for a diesel engine, with a displacement volume of 12.8 l or 14.8 l. The
spur gear drive 200 comprises a crankshaft gear 202 which drives a first
camshaft gear 212 and a second camshaft gear 214 via a first intermediate
gear 204, a second intermediate gear 206, a third intermediate gear 208
and a fourth intermediate gear 210. The first camshaft gear 212 serves
for controlling the inlet valves, and the second camshaft gear 214 serves
for controlling the outlet valves. The fourth intermediate gear 210 is
embodied as a distributor gear.

[0033]As in the first embodiment, an oil pump gear 216 is provided which
is situated, with respect to the camshaft axis (not shown), opposite the
camshaft gears 212, 214. However, the oil pump gear 216 is driven
directly by the crankshaft gear 202.

[0034]A compressor gear 220 is driven by the first intermediate gear 204.
A fuel pump gear 222 is driven by the second intermediate gear 206. A
turbocompound gear 224 is driven by a turbocompound intermediate gear
226.

[0035]In contrast to the first embodiment, in the spur gear drive 200, the
first intermediate gear 204 is a double gear, with the larger toothing
being in engagement with the crankshaft gear 202, and with the smaller
toothing driving the second intermediate gear 206 and the compressor gear
220. The second intermediate gear 206 is a single gear which is in
engagement with the fuel pump gear 222 and the third intermediate gear
208. The third intermediate gear 208 is again a double gear whose larger
toothing meshes with the second intermediate gear 206, with the smaller
toothing of the third intermediate gear 208 driving the fourth
intermediate gear 210.

[0036]In addition, the turbocompound intermediate gear 226 is embodied as
a double gear, with the larger toothing being in engagement with the
crankshaft gear 202 and the smaller toothing meshing with the toothing of
the turbocompound gear 224.

[0037]While the first camshaft gear 212, the second camshaft gear 214 and
the fourth intermediate gear 210 are mounted on a cylinder head (not
shown), the remaining gears are mounted on a gear transmission housing
228, with said gear transmission housing 228 preferably being formed in
one piece with the engine block.

[0038]In connection with FIG. 3 it is explained how a third intermediate
gear 208 can be arranged so as to be moveable with respect to an upper
edge 230 of an engine block or, respectively, a gear supported on the
cylinder head of the engine, which is shown in particular for the spur
gear drive 200 of the second embodiment shown in FIG. 2.

[0039]The third intermediate gear 208 is rotatably supported by a bearing
journal 232 which is mounted to the cylinder block (not shown--FIG. 3
shows the gear arrangement from the rear, that is the cylinder block
side) by mounting bolts 236. The bearing journal is held by a pin 234,
which extends into a bore in the cylinder block front wall and is
pivotally supported thereby. The bolts 236 extend through elongated holes
238 in the bearing journal 232 so that the bearing journal can be firmly
mounted to the cylinder block front wall by tightening of the bolts 236.
With the bolts 236 loosened the bearing journal 232 can be pivoted about
the pin 234 during assembly of the engine or in connection with a repair
for an adjustment of the distance between the axis of the intermediate
gear 208 and the fourth intermediate gear 210 which is mounted on the
cylinder head and consequently the tooth flank play of the two gears
which are in engagement with each other.